1. Field of the Invention
This invention relates to and has among its objects the provision of novel methods for extracting pigment from seeds containing the same, e.g., seeds of Bixa orellana L. (Lipstick Pod). It is a particular object of the invention to realize a high yield of pigment and to obtain seed which may be utilized as an animal feed after extraction of pigment therefrom. Further objects of the invention will be evident from the following description wherein parts and percentages are by weight unless otherwise specified.
2. Description of the Prior Art
The shrub Bixa orellana L. (Lipstick Pod) is native to tropical America and can be grown in moist climates such as in the tropical Americas, the Caribbean, East Africa, India, Pacific basin, Hawaii, Florida, etc. The plant and dye are known by various names, such as achiote (through much of Latin America), loa (Somoa), urucu (Brazil), and various other names such as roucou, onoto, bija, orlean, etc. The plant is large and quick-growing and produces clusters of pods, which, after drying, burst open to yield numerous small seeds. The plant is used both as an ornamental and as a source of pigment. The bright crimson outer covering of these seeds contains annatto, a natural pigment. After extraction from the seed covering, annatto is concentrated and used as a food coloring material for butter, cheese, chocolate, etc. The primary pigment in annatto is bixin; a yellow-red, carotenoid-type compound; in low concentration the annatto is yellow. Annatto is noncarcinogenic and, being a natural pigment, currently plays, and will continue to play, a prominent role as a food colorant.
Pigment is extracted from the seed of Lipstick Pod by a number of conventional procedures summarized in the East African Agricultural and Forestry Journal, Vol. 32, No. 2, pp. 126-132 (1966). Perhaps the oldest method involves leaching the seeds with either cold or hot water under agitating conditions. The pigment slurry is decanted and after boiling off excess water, an annatto paste is collected. This method has the disadvantages of being time-consuming, inefficient, and can cause deterioration of the pigment.
In another approach the seeds are washed with dilute aqueous alkali followed by water to yield a dark red solution, which is screened and acidified. The precipitated annatto pigment is collected, washed, and dried. The caustic extraction method has the advantage of extracting a large portion of the pigment in the seed. There are certain disadvantages associated with the alkaline extraction method. Alkali must be employed, thus necessitating a neutralization step to precipitate the solid dye. Furthermore, seed treated with caustic cannot be used directly as a poultry or animal feed, but first must be treated with acid to adjust the pH to an acceptable point.
Numerous solvent extractions are employed to extract the pigment from the seed. For example, Lipstick Pod seeds may be treated with edible oils, alkaline glycols, or volatile solvents, such as ethanol, acetone, trichloroethylene, etc., to extract pigment therefrom. After extraction is completed, the solvent is removed by distillation. These solvent extraction methods are expensive because of the quantity of solvent and elaborate equipment necessary for carrying out the extraction and distillation procedures and do not lend themselves to cottage-type industry or to farm level processing, customary in rural and undeveloped areas.